123 lines
5.2 KiB
Diff
123 lines
5.2 KiB
Diff
From: Matthias Schiffer <mschiffer@universe-factory.net>
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Date: Tue, 28 Mar 2017 14:40:20 +0200
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Subject: batman-adv: Keep fragments equally sized
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diff --git a/batman-adv/patches/1004-batman-adv-Keep-fragments-equally-sized.patch b/batman-adv/patches/1004-batman-adv-Keep-fragments-equally-sized.patch
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new file mode 100644
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index 0000000000000000000000000000000000000000..431c0b4a1a722c4c2ebae390bc0c90be18966023
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--- /dev/null
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+++ b/batman-adv/patches/1004-batman-adv-Keep-fragments-equally-sized.patch
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@@ -0,0 +1,112 @@
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+From 450247570eacc8b6cf5484fe61c50eff804c6416 Mon Sep 17 00:00:00 2001
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+Message-Id: <450247570eacc8b6cf5484fe61c50eff804c6416.1489082253.git.mschiffer@universe-factory.net>
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+From: Sven Eckelmann <sven@narfation.org>
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+Date: Sat, 4 Mar 2017 17:29:25 +0100
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+Subject: [PATCH] batman-adv: Keep fragments equally sized
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+MIME-Version: 1.0
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+Content-Type: text/plain; charset=UTF-8
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+Content-Transfer-Encoding: 8bit
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+
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+The batman-adv fragmentation packets have the design problem that they
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+cannot be refragmented and cannot handle padding by the underlying link.
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+The latter often leads to problems when networks are incorrectly configured
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+and don't use a common MTU.
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+
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+The sender could for example fragment a 1271 byte frame (plus external
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+ethernet header (14) and batadv unicast header (10)) to fit in a 1280 bytes
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+large MTU of the underlying link (max. 1294 byte frames). This would create
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+a 1294 bytes large frame (fragment 2) and a 55 bytes large frame
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+(fragment 1). The extra 54 bytes are the fragment header (20) added to each
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+fragment and the external ethernet header (14) for the second fragment.
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+
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+Let us assume that the next hop is then not able to transport 1294 bytes to
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+its next hop. The 1294 byte large frame will be dropped but the 55 bytes
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+large fragment will still be forwarded to its destination.
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+
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+Or let us assume that the underlying hardware requires that each frame has
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+a minimum size (e.g. 60 bytes). Then it will pad the 55 bytes frame to 60
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+bytes. The receiver of the 60 bytes frame will no longer be able to
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+correctly assemble the two frames together because it is not aware that 5
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+bytes of the 60 bytes frame are padding and don't belong to the reassembled
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+frame.
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+
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+This can partly be avoided by splitting frames more equally. In this
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+example, the 675 and 674 bytes large fragment frames could both potentially
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+reach its destination without being too large or too small.
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+
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+Reported-by: Martin Weinelt <martin@darmstadt.freifunk.net>
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+Fixes: db56e4ecf5c2 ("batman-adv: Fragment and send skbs larger than mtu")
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+Signed-off-by: Sven Eckelmann <sven@narfation.org>
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+Acked-by: Linus Lüssing <linus.luessing@c0d3.blue>
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+Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
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+---
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+ net/batman-adv/fragmentation.c | 20 +++++++++++++-------
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+ 1 file changed, 13 insertions(+), 7 deletions(-)
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+
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+diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
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+index c3e293a3..89882ed7 100644
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+--- a/net/batman-adv/fragmentation.c
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++++ b/net/batman-adv/fragmentation.c
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+@@ -396,7 +396,7 @@ out:
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+ * batadv_frag_create - create a fragment from skb
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+ * @skb: skb to create fragment from
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+ * @frag_head: header to use in new fragment
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+- * @mtu: size of new fragment
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++ * @fragment_size: size of new fragment
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+ *
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+ * Split the passed skb into two fragments: A new one with size matching the
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+ * passed mtu and the old one with the rest. The new skb contains data from the
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+@@ -406,11 +406,11 @@ out:
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+ */
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+ static struct sk_buff *batadv_frag_create(struct sk_buff *skb,
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+ struct batadv_frag_packet *frag_head,
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+- unsigned int mtu)
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++ unsigned int fragment_size)
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+ {
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+ struct sk_buff *skb_fragment;
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+ unsigned int header_size = sizeof(*frag_head);
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+- unsigned int fragment_size = mtu - header_size;
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++ unsigned int mtu = fragment_size + header_size;
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+
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+ skb_fragment = netdev_alloc_skb(NULL, mtu + ETH_HLEN);
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+ if (!skb_fragment)
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+@@ -448,7 +448,7 @@ bool batadv_frag_send_packet(struct sk_buff *skb,
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+ struct sk_buff *skb_fragment;
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+ unsigned int mtu = neigh_node->if_incoming->net_dev->mtu;
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+ unsigned int header_size = sizeof(frag_header);
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+- unsigned int max_fragment_size, max_packet_size;
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++ unsigned int max_fragment_size, num_fragments;
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+ bool ret = false;
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+
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+ /* To avoid merge and refragmentation at next-hops we never send
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+@@ -456,10 +456,15 @@ bool batadv_frag_send_packet(struct sk_buff *skb,
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+ */
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+ mtu = min_t(unsigned int, mtu, BATADV_FRAG_MAX_FRAG_SIZE);
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+ max_fragment_size = mtu - header_size;
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+- max_packet_size = max_fragment_size * BATADV_FRAG_MAX_FRAGMENTS;
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++
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++ if (skb->len == 0 || max_fragment_size == 0)
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++ return -EINVAL;
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++
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++ num_fragments = (skb->len - 1) / max_fragment_size + 1;
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++ max_fragment_size = (skb->len - 1) / num_fragments + 1;
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+
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+ /* Don't even try to fragment, if we need more than 16 fragments */
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+- if (skb->len > max_packet_size)
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++ if (num_fragments > BATADV_FRAG_MAX_FRAGMENTS)
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+ goto out_err;
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+
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+ bat_priv = orig_node->bat_priv;
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+@@ -480,7 +485,8 @@ bool batadv_frag_send_packet(struct sk_buff *skb,
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+
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+ /* Eat and send fragments from the tail of skb */
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+ while (skb->len > max_fragment_size) {
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+- skb_fragment = batadv_frag_create(skb, &frag_header, mtu);
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++ skb_fragment = batadv_frag_create(skb, &frag_header,
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++ max_fragment_size);
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+ if (!skb_fragment)
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+ goto out_err;
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+
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+--
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+2.12.0
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+
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